This invention is directed to intravascular systems for corporeal cooling. More particularly, this invention is directed to catheter systems that have features that are especially useful for cooling organs, tissue, or limbs.
It has been found that cooling of the central nervous system provides many advantages in dealing with neurological problems. Beneficial results have been obtained from hypothermia of the intracranial structures in surgical treatment of certain brain tumors, cerebrovascular lesions such as aneurysms and hemangiomas, and head injuries. Hypothermia of the intracranial structures results in a decrease in brain volume and cerebral blood flow, as well as the arrest of cerebral edema when present. Furthermore, when the tissue of the central nervous system cools, there is a decrease in oxygen consumption and, therefore, greater protection against anoxia during deficient or arrested circulation. In addition, the resistance of brain tissue to surgical trauma is markedly increased and surgical bleeding is easy to control. Thus, local or regional hypothermia of the central nervous system is effective as a therapeutic technique, per se, as a surgical aid and also as a post-operative technique.
Cerebral hypothermia in the past has been brought about by cooling the entire body (surface cooling and intravascular perfusion), cooling the vascular supply to the brain, regional hypothermia by extracorporeal intravascular perfusion, or by the use of cold capsules or ice applied directly to the cerebral hemispheres. Systemic hypothermia by intravascular perfusion requires an additional major surgical procedure and carries with it a number of complications. A serious complication sometimes experienced through the use of systemic hypothermia (surface or intravascular) is ventricular fibrillation and cardiac asystole, which is attributable to the lower temperature tolerance of heart neuromuscular elements, as compared with central nervous system tissue.
There are a number of intravascular systems that are presently used for corporeal cooling, especially brain cooling. However, it has been found that there are certain disadvantages when such systems are used, and there is a definite need for improved systems.
It is an object of the invention to provide intravascular systems useful for corporeal cooling, especially cooling the brain or other organs, such as the kidneys.
It is also an object of the invention to provide an intravascuar system for corporeal cooling that has a pressure dependent valve.
It is a further object of the invention to provide a method for treating stroke patients where the patients are treated by brain cooling shortly after the stroke event to minimize insult and/or damage.
It is yet a further object of the invention to provide an intravascular system having balloons with variable inflation.
It is an additional object of the invention to provide an insulated intravascular system.
It is a still further object of the invention to provide an intravascular system having variable fenestration.
It is likewise an object of the invention to provide an intravascular system for cooling organs, tissue, or limbs.
It is a yet further object of the invention to provide an intravascular system for delivering drugs or other fluids to a desired corporeal location.
These and other objects of the invention will become more apparent from the discussion below.
In an intravascular brain cooling procedure, a catheter is advanced into the common carotid artery and the distal tip of the catheter is positioned within the internal carotid artery. Preferably the distal tip of the catheter has one or more inflatable balloons or other structures to obstruct the annular space between the outer surface of the catheter and the inner surface of the internal carotid artery. Cooled blood is provided to the brain through one or more lumens in the catheter.
A catheter for corporeal cooling may have a pressure sensitive valve to provide relief in the event of pressure build-up within the catheter. Also, the catheter may be insulated to avoid systemic cooling and related cardiac complications. At the proximal section of a corporeal cooling catheter system where the patient""s blood is removed for cooling, an outer catheter sheath may comprise variable fenestrations to facilitate blood withdrawal. Optionally a catheter according to the invention may have one or more pressure sensors to sense blood pressure within or without the catheter.
In addition, it has been found that brain cooling may be beneficial when applied to stroke patients. Further, cooling a kidney by providing cooled blood into a renal artery can be effective in treating renal failure.